Book Review: Doing good for Darwin

As We Know It is the antidote to most pop science books in three respects, since it is funny, sane and disorganised. The ideal work of pop biology starts with a heroic researcher, crouched, perhaps, among giant fossilised dinosaur turds. He stumbles on a soundbite that will revolutionise his field: a theory that can be expressed in 20 words at most and then applied to explain everything that modern humans do, from shopping to the other thing. The explanation will widen through subsequent chapters, applied with iron consistency and never meeting any serious problems, until the final, quasi-religious peroration breaks into undiluted kitsch about the future - a prose equivalent of John Lennon's song "Imagine".

Marek Kohn's book is not in the least like that. It leaves you with a head stuffed full of fascinating questions, and the uneasy sense that hard thought and patient experiment will be required to find the answers. It was said of Richard Dawkins's The Selfish Gene that it made the reader feel like a genius (though it is a better book than that praise suggests). As We Know It makes the reader feel like a bewildered scientist, which is perhaps a more realistic perspective on the problems of human evolution.

It is a survey of theories of how the human mind may have evolved from whatever it was that our ancestors had when they came out of the forest on their hands and knees. The good reason these theories are suddenly fashionable is that, in the cluster of ideas known as sociobiology or selfish genery, there suddenly emerged in the late Sixties and early Seventies some hard mathematical reasons to explain why some things just can't happen in a Darwinian system.

Two streams of thought came together with one discovery to make this possible. Game theory, developed after 1945, made it possible to analyse mathematically the ways in which strategies of behaviour interact. Ethology studied the ways in which animals' behaviour was as much an adaptation to their environment as their bodies are, so that a bird's song is as much a way of manipulating the world as its wings. And the mathematical formulae of W D Hamilton and George Price made it not just clear, but measurable, how "altruistic" behaviour could spread through a population even if it damaged the bearer, provided that the genes which would in some circumstances trigger this behaviour were shared by other animals which would benefit by it.

The first thing to be said about this stuff is that it's true. There are vicious disagreements about the rhetoric and philosophical penumbra surrounding some of these ideas. But neo-Darwinism, or sociobiology, really is the only game in town. The idea that some kinds of historical change can be mathematically analysed - an extension of geometry from space to time - is irresistible. The trouble is that it does not tell us very much about culture, which is where we live.

Selfish genery does not just supply a tool-kit for thinking about behaviour, though that is part of its attraction. One unspoken assumption of the theory, which has become clearer over the past 20 years, is that what we experience as emotions can just as well be analysed as strategies. This is the point at which human sociobiology, or "evolutionary psychology" as it is now known, has done its best and worst.

The worst is "Flintstones anthropology", in which the biases of the reader can be justified by reference to an idyllic Stone Age for which we were designed to function. The best produces clearly argued explanations for features of human character so fundamental that we never realised they needed explaining, such as our sense of fairness. The real explanatory power of sociobiology is not that it shows that All Men Are Bastards, but that it explains how men and women are for the most part not bastards at all; and how their genuinely benevolent emotions have emerged in a Darwinian world.

The theory of this is easy to grasp; much of it is based on sexual selection. The practical workings out are much harder. They come down to one question. Why are we not all Jonathan Aitkens? Why do most people, even Etonians, generally tell the truth and stay reasonably faithful?

The dual nature of emotion and strategy is crucial here. Within an individual, we talk about emotion and calculation, or strategy, as opposites. But looking at a species as a whole, any sufficiently widespread pattern of emotion, if analysed as a strategy, allows one to deduce the kind of society in which it made sense. Just as an animal with large wings can be presumed to spend a lot of time in the air, an animal with the capacity for benevolence, for religious devotion and for the appreciation of art which we undoubtedly have must have evolved this emotional constitution in an environment where it was beneficial. This means, most importantly, an environment in which cheating did not pay, or at least paid no better than honesty in the long run.

A large portion of this book considers recent attempts to reconstruct this environment, in which the route to sexual success lay through intelligence and a reasonable degree of trustworthiness rather than brute force and treachery. The evidence that we have for most of prehistory is hand-axes, and Kohn produces a dazzling meditation on what these axes might have meant to users; how they might have functioned as tools and signs, scrapers of flesh and hewers of status.

This is model science writing: clear, conscientious and exciting, showing both what we know and what we don't. The practical experiments and the theory illuminate and balance each other beautifully. Anyone interested in human evolution should read it.

But there is a problem. Ignorance will always expand to encompass our knowledge and, for much of his account of human origins, Kohn is simply describing contending theories between which there is no good way to judge. The experiments have yet to be done, and possibly thought of. It's not his fault Science has not come up with the answers; and it's a great merit that he is so honest about it. Perhaps it was simply too early to write a history of these ideas; but then part of his purpose is clearly polemical - to rescue sociobiology from the Right - and the two aims don't fit entirely happily together.

Andrew Brown's 'The Darwin Wars' is published by Simon & Schuster